I am about to build out this system and need some advice.

BB.

No problem.

Are you sure that is Vmp, and not Voc?. Typical Vmp for "12 volt" panels would be around 18.0 volts.

-Bill

mcgivor

Rv_Adventure_Couple said:

mcgivor said:

The  BMS needs to be connected directly to the battery  negative in order to provide protection, the shunt should be downstream of the BMS, failure to do this will negate all protection if the connection of the shunt were to fail .

Should the BMS be incapable of supporting the required current then a suitable one should be sourced, don't mess around attempting to bypass the safety features, that would be a fools game. The BMS needs to have priority, that can only be achieved if it is first in line, better yet get a bi directional BMS with separate charging and dischargeing ports, they can be had for around  $100 

I have revised the diagram, am I correct in this draw up?

That's better, what charge controller do you intend to use? Parrallel connection is not an option if the VMP is below ~30V and the controller needs to be programmable as  LiFePo4 have different voltage and charging stages than lead acid, this is important to understand.

The array even at 800W would be undesized if a large portion of the capacity were used, of course location will be a factor as well, flat mounted in the tropics is fine but performance is reduced the further north or south yout go, just some food for thought.

Rv_Adventure_Couple

BB. said:

No problem.

Are you sure that is Vmp, and not Voc?. Typical Vmp for "12 volt" panels would be around 18.0 volts.

-Bill

Here is the sticker on the back of my panels

Rv_Adventure_Couple

mcgivor said:

Rv_Adventure_Couple said:

mcgivor said:

The  BMS needs to be connected directly to the battery  negative in order to provide protection, the shunt should be downstream of the BMS, failure to do this will negate all protection if the connection of the shunt were to fail .

Should the BMS be incapable of supporting the required current then a suitable one should be sourced, don't mess around attempting to bypass the safety features, that would be a fools game. The BMS needs to have priority, that can only be achieved if it is first in line, better yet get a bi directional BMS with separate charging and dischargeing ports, they can be had for around  $100 

I have revised the diagram, am I correct in this draw up?

That's better, what charge controller do you intend to use? Parrallel connection is not an option if the VMP is below ~30V and the controller needs to be programmable as  LiFePo4 have different voltage and charging stages than lead acid, this is important to understand.

The array even at 800W would be undesized if a large portion of the capacity were used, of course location will be a factor as well, flat mounted in the tropics is fine but performance is reduced the further north or south yout go, just some food for thought.

I have a epever tracer 150v/40 mppt 12/24 charge controller and it is programmable. I want to add more panels just later after this purchase round.

BB.

Hmmm... That looks like a 36 Cell panel, which would be Vmp~18 volts. But, their panels, their specs.

Note that you still have your cells in groups of 2x (parallel). Your 24 volt bank, needs all the cells wired in series for 24 volts.

-Bill

BB.

Hmmm... That looks like a 36 Cell panel, which would be Vmp~18 volts. But, their panels, their specs.

Note that you still have your cells in groups of 2x (parallel). Your 24 volt bank, they will all be in series.

-Bill

Rv_Adventure_Couple

BB. said:

Hmmm... That looks like a 36 Cell panel, which would be Vmp~18 volts. But, their panels, their specs.

Note that you still have your cells in groups of 2x (parallel). Your 24 volt bank, needs all the cells wired in series for 24 volts.

-Bill

Yea with my current CC I will have to series / parallel when I get 2 more panels for the total of 800 watts.

Rv_Adventure_Couple

mike95490 said:

If an inverter is capable of burning up a BMS, then the battery bank/BMS (they work as a pair) is too small or the inverter too big.

 a 3Kw inverter on a 12V system is STUPID DANGEROUS.  3Kw at 12V 90% efficient is 275 amps. I defy you to find a 12V 3kw inverter under $500, that has internal wiring that is safe at nearly 300A.

Have you heard anything bad about this inverter?

https://www.amazon.com/gp/product/B00BXTOQD4/ref=ox_sc_saved_title_2?smid=A29YHE8OKANI0B&psc=1

softdown

I'd take a look at this one. Samlex is more highly regarded: https://www.amazon.com/Samlex-1500W-Pure-Sine-Inverter/dp/B00AYH68K0/ref=sr_1_4?dchild=1&keywords=1500+watt+pure+sine+wave+inverter+24+volt&qid=1587145196&s=electronics&sr=1-4

Too big of inverter, too much battery and not enough panels creates a lot of disappointments.

BB.

I really do not give "product ratings". First, because I am not in the business and do not use the units--And second, because of my luck, I would say A, and somebody would have an F experience.

Best I can do is relate issues that I seen and have read about... AIMs inverters are known for the 6+ kWatt @ 12 volt units--Which is just about impossible to reliably pull from a 12 volt battery bank.

We had one poster here that was running a metal fabrication (arc welders, saws, etc. which are all "difficult" loads for inverters) shop off of "recovered" forklift batteries and AIMs inverters--And he was very happy with both the batteries and his AIMs inverters.

Second, I ran "fakespot" on this Amazon listing, and the listing (and AIMs) came up with a B score for review "quality"--That ain't bad.

https://www.fakespot.com/

Third, in general, AIMs is not very expensive, and this inverter is an Inverter-Charger... Does not use a high amount of Tare loading for its 2 kWatt rating (12 Watts).

It has good features:

FEATURES: GFCI outlet, AC direct connect terminal block, charge current control dial, dip switches to set priorities, auto gen start, conformal coated, power save mode and battery temp sensor. Only one set of cables needed. Optional remote available.

Supports multiple battery chemistry types. Has automatic 120 VAC transfer switch, and remote on/power save/off panel...

But you do have to read the manual:

https://images-na.ssl-images-amazon.com/images/I/B1TWGoAjYVS.pdf

For example, the 12 Watts is in "Power Save"... The Tare loss when "on" is somewhere around 27 Watts (typical for size of inverter). Where this kills you is, for example running a laptop and led desk lamp... Say 30 Watts + 5 Watts = 35 Watts... The inverter itself is using 27 Watts or just a little bit less than your "smaller" loads... Efficiency is would be around (35w/62w=0.56) ~56% efficiency...

Other than it, may be, oversized for your "typical loads" (excluding running A/C for an hour), in my humble opinion, assuming it works as advertizes, and you have read through the manual--It looks like it tick's all of your boxes for a low cost.

If it lasts for 5+ years and runs your loads as needed, what more can you ask for.

A similar feature set, "high end" Outback sealed inverter is ~$1,640 (the output includes Grid Tied inverter function, but you probably do not need/want this for the RV)... Even if you have to buy a new AIMs every 5 years, you probably will come ahead $$$ wise...

https://www.solar-electric.com/outback-power-fxr2524a-hybrid-inverter.html

Research/read about what is out there before making your purchases. Paper designs are much easier to change vs after you bought the hardware.

-Bill

Rv_Adventure_Couple

BB. said:

I really do not give "product ratings". First, because I am not in the business and do not use the units--And second, because of my luck, I would say A, and somebody would have an F experience.

Best I can do is relate issues that I seen and have read about... AIMs inverters are known for the 6+ kWatt @ 12 volt units--Which is just about impossible to reliably pull from a 12 volt battery bank.

We had one poster here that was running a metal fabrication (arc welders, saws, etc. which are all "difficult" loads for inverters) shop off of "recovered" forklift batteries and AIMs inverters--And he was very happy with both the batteries and his AIMs inverters.

Second, I ran "fakespot" on this Amazon listing, and the listing (and AIMs) came up with a B score for review "quality"--That ain't bad.

https://www.fakespot.com/

Third, in general, AIMs is not very expensive, and this inverter is an Inverter-Charger... Does not use a high amount of Tare loading for its 2 kWatt rating (12 Watts).

It has good features:

FEATURES: GFCI outlet, AC direct connect terminal block, charge current control dial, dip switches to set priorities, auto gen start, conformal coated, power save mode and battery temp sensor. Only one set of cables needed. Optional remote available.

Supports multiple battery chemistry types. Has automatic 120 VAC transfer switch, and remote on/power save/off panel...

But you do have to read the manual:

https://images-na.ssl-images-amazon.com/images/I/B1TWGoAjYVS.pdf

For example, the 12 Watts is in "Power Save"... The Tare loss when "on" is somewhere around 27 Watts (typical for size of inverter). Where this kills you is, for example running a laptop and led desk lamp... Say 30 Watts + 5 Watts = 35 Watts... The inverter itself is using 27 Watts or just a little bit less than your "smaller" loads... Efficiency is would be around (35w/62w=0.56) ~56% efficiency...

Other than it, may be, oversized for your "typical loads" (excluding running A/C for an hour), in my humble opinion, assuming it works as advertizes, and you have read through the manual--It looks like it tick's all of your boxes for a low cost.

If it lasts for 5+ years and runs your loads as needed, what more can you ask for.

A similar feature set, "high end" Outback sealed inverter is ~$1,640 (the output includes Grid Tied inverter function, but you probably do not need/want this for the RV)... Even if you have to buy a new AIMs every 5 years, you probably will come ahead $$$ wise...

https://www.solar-electric.com/outback-power-fxr2524a-hybrid-inverter.html

Research/read about what is out there before making your purchases. Paper designs are much easier to change vs after you bought the hardware.

-Bill

Thank you sir. I will probably go with the AIMs, eventually put 2 more panels on the roof, and maybe add another 150ah at 24v. Just need to see how the system works. Just trying real hard to not buy tings twice.

Rv_Adventure_Couple

softdown said:

I'd take a look at this one. Samlex is more highly regarded: https://www.amazon.com/Samlex-1500W-Pure-Sine-Inverter/dp/B00AYH68K0/ref=sr_1_4?dchild=1&keywords=1500+watt+pure+sine+wave+inverter+24+volt&qid=1587145196&s=electronics&sr=1-4

Too big of inverter, too much battery and not enough panels creates a lot of disappointments.

Thanks for the input, but the diagram isnt the end game. I am just building in stages and trying to size things for what it will be and not what you see. I will add 400 more watts of solar and most likely add another 150ah at 24v of lifepo4

littleharbor2

 The 40 amp rating is the output rating. You really need to series wire and bring up the input voltage for the controller to do its MPPT thing.

 As to the BMS, I'm not familiar with these, or lithium batteries for that matter. Does it even need to be inline with the charging circuit? Also as to a connection failure, it seems highly unlikely that the robust connections on the shunt would be failure prone, provided they are torqued correctly. What gauge wire is on the BMS? The way you have drawn the latest diagram, the BMS will need to be able to handle the potential current draw from the inverter at full surge current.

mcgivor

littleharbor2 said:

 The 40 amp rating is the output rating. You really need to series wire and bring up the input voltage for the controller to do its MPPT thing.

 As to the BMS, I'm not familiar with these, or lithium batteries for that matter. Does it even need to be inline with the charging circuit? Also as to a connection failure, it seems highly unlikely that the robust connections on the shunt would be failure prone, provided they are torqued correctly. What gauge wire is on the BMS? The way you have drawn the latest diagram, the BMS will need to be able to handle the potential current draw from the inverter at full surge current.

The BMS not only controls the charging but also the discharging current, with protection against short circuit, overcurrent, over/under voltage etcetera, so it needs to have priority and yes it needs to be capable of handling all expected parameters.

The image below is the configuration for the BMS I have, it is perhaps slightly different in that ir has separate ports to allow bypass current to flow to the loads independent of the battery itself but the concept is the same. The attached pdf shows the protection it provides so if it unable to see the loads, some of the protection would be lost and because serious damage could occur, it's important to have these protectionsin place.

Hope this information is helpful in providing some insight to the importance of how and where a BMS should be installed.

softdown

littleharbor2 said:

 The 40 amp rating is the output rating. You really need to series wire and bring up the input voltage for the controller to do its MPPT thing.

 As to the BMS, I'm not familiar with these, or lithium batteries for that matter. Does it even need to be inline with the charging circuit? Also as to a connection failure, it seems highly unlikely that the robust connections on the shunt would be failure prone, provided they are torqued correctly. What gauge wire is on the BMS? The way you have drawn the latest diagram, the BMS will need to be able to handle the potential current draw from the inverter at full surge current.

The panels will largely dictate the ultimate voltage fed to the charge controller. Somewhere between ~ 35 and 60 volts would be good. Think I have seen ~40 volts parried about as "close to ideal". Pretty rusty there. Perhaps 70 volts would also be fine?

mike95490

So, the panel Vmp string voltage, generally is happy at 2x battery voltage. This gives the MPPT circuit something to work with, too low of voltage and the MPPT may not function, too high and you exceed the input voltage rating of the MPPT and the magic smoke is released.
Most good MPPT controllers have a "String Sizer" which balances your panel configuration with your seasonal high and low temps, and validates or condemns your plan.
http://www.midnitesolar.com/sizingTool/index.php

softdown

With a 150 volt charge controller (Outback FM80) I could have used either ~80 or ~120 incoming volts. Some of us "enjoy" cold climates and must concern ourselves with an esoteric concept called Hyper VOC. Wherein very cold weather can drive up system voltage to a level that sends your beloved charge controller - "interstellar". It starts happening below 0F as memory serves. For those who can see temps well below 0F they had best pay heed to the risk. 

Since I can see -30F I was confined to two panels in serial connections. One, maybe two, posters noted that ~80 volts was "perfect" anyway. Though I could have used fewer combiner boxes and less wiring with three panels per box instead of two. 

Not the best link but it helps. I think Midnite coined the term Hyper VOC while Outback prefers such endearing terms as "invalidated warranty". http://midniteftp.com/forum/index.php?topic=271.0

There are many who would argue that I could have done  ~120 volts (three serial panels) but I deferred to Outbacks stern warning. I figure they have some experience. 

Lower volts does translate to more amps I believe. Another thing to consider. Think I have seen that anyway. Been a day since I was staring at my charge controller. 

littleharbor2

mcgivor said:

littleharbor2 said:

 The 40 amp rating is the output rating. You really need to series wire and bring up the input voltage for the controller to do its MPPT thing.

 As to the BMS, I'm not familiar with these, or lithium batteries for that matter. Does it even need to be inline with the charging circuit? Also as to a connection failure, it seems highly unlikely that the robust connections on the shunt would be failure prone, provided they are torqued correctly. What gauge wire is on the BMS? The way you have drawn the latest diagram, the BMS will need to be able to handle the potential current draw from the inverter at full surge current.

The BMS not only controls the charging but also the discharging current, with protection against short circuit, overcurrent, over/under voltage etcetera, so it needs to have priority and yes it needs to be capable of handling all expected parameters.

The image below is the configuration for the BMS I have, it is perhaps slightly different in that ir has separate ports to allow bypass current to flow to the loads independent of the battery itself but the concept is the same. The attached pdf shows the protection it provides so if it unable to see the loads, some of the protection would be lost and because serious damage could occur, it's important to have these protectionsin place.

Hope this information is helpful in providing some insight to the importance of how and where a BMS should be installed.

Thanks for the info. Lithium is still a chemistry I am unsure about. I just replaced my battery bank so maybe in 5 years or so there will be big advances in production and they will become more affordable.

softdown

littleharbor2 said:

mcgivor said:

littleharbor2 said:

 The 40 amp rating is the output rating. You really need to series wire and bring up the input voltage for the controller to do its MPPT thing.

 As to the BMS, I'm not familiar with these, or lithium batteries for that matter. Does it even need to be inline with the charging circuit? Also as to a connection failure, it seems highly unlikely that the robust connections on the shunt would be failure prone, provided they are torqued correctly. What gauge wire is on the BMS? The way you have drawn the latest diagram, the BMS will need to be able to handle the potential current draw from the inverter at full surge current.

The BMS not only controls the charging but also the discharging current, with protection against short circuit, overcurrent, over/under voltage etcetera, so it needs to have priority and yes it needs to be capable of handling all expected parameters.

The image below is the configuration for the BMS I have, it is perhaps slightly different in that ir has separate ports to allow bypass current to flow to the loads independent of the battery itself but the concept is the same. The attached pdf shows the protection it provides so if it unable to see the loads, some of the protection would be lost and because serious damage could occur, it's important to have these protectionsin place.

Hope this information is helpful in providing some insight to the importance of how and where a BMS should be installed.

Thanks for the info. Lithium is still a chemistry I am unsure about. I just replaced my battery bank so maybe in 5 years or so there will be big advances in production and they will become more affordable.

How are things in Baja with this C-19 thing? Have you retired there yet? 

My lithium math says they last ~ 3 times as long and cost ~ 3 times more. Since life brings so many changes, the math has yet to rationalize the leap to lithium. 

Then we have these Chinese lithium 18650's to consider: https://www.youtube.com/watch?v=qMZuHMlRw_0
The Chinese batteries are junkie. 
To be fair, Chinese factories frequently just supply requests from international marketers - who are free to claim anything they want. Much to be said for buying from reputable companies like Sony or Samsung. I would want a recognizable name on an $800 battery. 

I'm not aware of anyone here with more than a few years of lithium solar battery experience under their belt. What if many of them started catching fire after a decade or so? 

mcgivor

softdown said:

littleharbor2 said:

mcgivor said:

littleharbor2 said:

 The 40 amp rating is the output rating. You really need to series wire and bring up the input voltage for the controller to do its MPPT thing.

 As to the BMS, I'm not familiar with these, or lithium batteries for that matter. Does it even need to be inline with the charging circuit? Also as to a connection failure, it seems highly unlikely that the robust connections on the shunt would be failure prone, provided they are torqued correctly. What gauge wire is on the BMS? The way you have drawn the latest diagram, the BMS will need to be able to handle the potential current draw from the inverter at full surge current.

The BMS not only controls the charging but also the discharging current, with protection against short circuit, overcurrent, over/under voltage etcetera, so it needs to have priority and yes it needs to be capable of handling all expected parameters.

The image below is the configuration for the BMS I have, it is perhaps slightly different in that ir has separate ports to allow bypass current to flow to the loads independent of the battery itself but the concept is the same. The attached pdf shows the protection it provides so if it unable to see the loads, some of the protection would be lost and because serious damage could occur, it's important to have these protectionsin place.

Hope this information is helpful in providing some insight to the importance of how and where a BMS should be installed.

Thanks for the info. Lithium is still a chemistry I am unsure about. I just replaced my battery bank so maybe in 5 years or so there will be big advances in production and they will become more affordable.

How are things in Baja with this C-19 thing? Have you retired there yet? 

My lithium math says they last ~ 3 times as long and cost ~ 3 times more. Since life brings so many changes, the math has yet to rationalize the leap to lithium. 

Then we have these Chinese lithium 18650's to consider: https://www.youtube.com/watch?v=qMZuHMlRw_0
The Chinese batteries are junkie. 
To be fair, Chinese factories frequently just supply requests from international marketers - who are free to claim anything they want. Much to be said for buying from reputable companies like Sony or Samsung. I would want a recognizable name on an $800 battery. 

I'm not aware of anyone here with more than a few years of lithium solar battery experience under their belt. What if many of them started catching fire after a decade or so? 

We all know too well of the stalwart belief that lead acid is a proven technology, albeit being out of date by perhaps 20 years, the pioneers are not affiliated with this forum, but rather with more progressive users in other locations.

Sometimes it takes those who think outside the restrictive box to provide information to the unbelievers that something actually has its advantages, there are many who have multiple years of recorded success with lithium technology  if you care to venture outside this restrictive box you've created in denial, don't criticize what you don't understand, as Bob Dylan once said

softdown

Let's see what you say when carbon battery's are available in ~ 5 years. I suspect you may  say "I'll wait and see. My lithium battery's are doing fine."

I didn't criticize lithium, I said I'll wait awhile longer. Why not? I hope to get four more years from what I have. 

I know lithium is better and I explained the economies of my thinking pretty clearly. It takes a real long time to break even. 

littleharbor2

softdown said:

How are things in Baja with this C-19 thing? Have you retired there yet? 

Baja is wonderful right now. The ex-pat community are practicing safe social distancing, though many of us have been here over a month without any outside influence so we do have limited social interaction amongst friends. The beach and desert haven't changed so we still can jump on our vehicle of choice and get out in the sun and fresh air.

I have now fully retired and plan to spend the rest of my days here. 

mcgivor

@littleharbor2 That looks like south of San Felipe, if so how far south? 

BB.

On our local beaches, tickets. And if you are >5 miles away, more tickets:

https://www.foxnews.com/us/california-coronavirus-stay-at-home-beach-order-citation-san-mateo

Last month, San Mateo County Health Officer Scott Morrow issued an order prohibiting from outdoor recreational activity outside a five-mile radius of an individual's residence. Pacifica Mayor Deirdre Martin said the data shows that "many are not taking these orders seriously."

I spent my first 29 years in Pacifica... Not happy with these "orders".

-Bill

littleharbor2

littleharbor2 said:

softdown said:

How are things in Baja with this C-19 thing? Have you retired there yet? 

Baja is wonderful right now. The ex-pat community are practicing safe social distancing, though many of us have been here over a month without any outside influence so we do have limited social interaction amongst friends. The beach and desert haven't changed so we still can jump on our vehicle of choice and get out in the sun and fresh air.

I have now fully retired and plan to spend the rest of my days here. 

This is 25 miles from town. About K 33

littleharbor2

BB. said:

On our local beaches, tickets. And if you are >5 miles away, more tickets:

https://www.foxnews.com/us/california-coronavirus-stay-at-home-beach-order-citation-san-mateo

Last month, San Mateo County Health Officer Scott Morrow issued an order prohibiting from outdoor recreational activity outside a five-mile radius of an individual's residence. Pacifica Mayor Deirdre Martin said the data shows that "many are not taking these orders seriously."

I spent my first 29 years in Pacifica... Not happy with these "orders".

-Bill

I'd be bummed too. Nice to live on the beach, that's for sure. Reminds me of a sign at my next door neighbor's place....If you're lucky enough to live at the beach, You're lucky enough.

BB.

We used to have a few small clubs and small housing right on the beach... But over the decades, the city/state has worked to remove much of that through regulation and buyouts (not that building on sand next to the Pacific Ocean just above high tide was ever a "brilliant" idea).

-Bill

softdown

Local state park closed with backhoe! Doesn't look like Colorado plans to re-open. Three different city, state and Ingsoc patrol vehicles at a small town post office. Right now 2020 is 1984.